Advanced signalling examples

From OpenTTD

For general information about signals, and instructions on how to build them, see the main signals article

To Do
Tidy this up into a proper showcase of complicated signalling arrangements. Maybe even export it all to new types of Junctions or into Stations.

Fig 3. - Pre-signals used to their full potential.

To Do
Label the above image and explain what's going on

[edit] Optimal pre-signalled station

Below is an image of an "optimal" Pre-signal station layout. With these signals trains will choose any free platform and if none is free it will wait at the entrance instead of brutally picking one and waiting for that train to leave.

Fig. 4 - An "optimal" RoRo station layout with presignals.

Explanation of the signal types:

• Signals 1 through 12 are Pre-signal Exits
• Signals A, B, C and D are Combo Signals
• The signal E is the only Pre-signal (Entrance)

How they operate:

• If signals 1, 2, 3 and 4 are red then signal A will be red.
• If signals 5, 6, 7 and 8 are red then signal B will be red.
• If signals 9, 10, 11 and 12 are red then signal D will be red.
• If any train is between signal A and signals 1, 2, 3 and 4 signal A will be red.
• If any train is between signal B and signals 5, 6, 7 and 8 then signal B will be red.
• If any train is between signal C and signals A and B then signal C will be red.
• If any train is between signal D and signals 9, 10, 11 and 12 then signal D will be red.
• If any train is between signal E and signals D and C then signal E will be red.
• If signals A and B are red then signal C will be red.
• If signals C and D are red then signal E will be red preventing access to the station.

Below is an animation of how this would work in the game.

Fig. 5 - How the "optimal" RoRo station would work with presignals.

As the animation shows trains can choose any track without too many problems.

[edit] Another example

Fig. 6 - Station with presignals.

[edit] Free tracks

Using presignals to allow trains to use spare tracks more intelligently

Suppose you have two tracks leading from two sources to the same location. You want each source's own traffic to have priority on its own track but want to utilise spare capacity on one of the tracks because the other is getting busy. This can be achieved with presignals.

In the diagram, the two tracks are labelled A and B leading into tunnels A and B respectively. Track A is the one with a less frequent service whose spare capacity we want to use. Track B is very busy and needs some breathing space, which we can get by diverting traffic onto A. However, what we don't want to do is let B's traffic disrupt the service on A - in other words A needs priority on its own tunnel. We arrange this by using presignals.

Assume each of the tunnels is signalled at the opposite end so that when a train leaves the tunnel the signals at this end clear. So signal 1 will show green when tunnel B is clear, which will in turn make entry presignal 4 green. The interesting part comes when tunnel B is blocked, so 1 is red. In that case we want an incoming train to use tunnel A, but only if there isn't a train on track A wanting to use it.

We connect the tracks as shown and place signal 3 as an exit signal to 4 so that a train coming up to 4 can use either 3 or 1, whichever is available. Now, we need to stop 3 showing green if a train on A needs to use the tunnel. To do this we simply make signal 2 a bi-directional exit signal. Then if there is a train in the block before it on A (i.e. one with priority on the tunnel), the back of the signal will show red, otherwise it will of course be green. Then, if we make 3 a combo signal, it will show red in two cases:

1. A train is in tunnel A
2. There is a train on track A coming up to use the tunnel that should be given priority (because signal 2 will be red and it appears as an exit to 3 even though that isn't possible with the track layout)

So when 3 is red, a train on B is only allowed to proceed on its own track.

In that way, trains on B use track A if there is spare capacity but any vehicles already on A get priority.

Translation:進階信號配置法(zh-TW)